Polymer matrix with three-dimensional network
The lignin is the main component of the cellular wall and is produced by the lignification process that leads to the draining of the protoplasm of alive cells and the building of secondary cellular walls (the so-called “cell death”).
The lignin is a complex three-dimensional polymer whose chemical bonds have not been fully identified and it is difficult to isolate. According to many studies the base element is an aromatic structure of the type phenyl-propane (therefore it is not a carbohydrate but has a polyphenolic nature) from which some « forerunners » through a spatial complex cross-linkage produced by enzymatic reactions that formed a molecular three-dimensional but not crystalline structure.
On an anhydrous wood sample from a conifer or a broadleaf tree the cellulose makes the 50 % of the total weight, whereas the hemicellulose constitutes between 15-35% and the 20% of the weight in broadleaves and conifer trees respectively and in the lignin the weight percentage of the weight is between 25-35% in conifer trees and 17-25% in broadleaf trees.